TCEQ USGS Topographic Map Viewer Help Page
- What is the TCEQ USGS Topographic Map Viewer?
- Getting Started
- How Do I Find the Name of a Particular Map Feature?
- What Do "Visible" and "Active" Mean?
- Obtaining a Latitude and Longitude
- Navigation Tools: Moving Around Within the Map
- Measuring the Distance Between Points
- Selecting Features and Making Database Queries
- How Do I Print Out a Copy of my Map?
- Zoom To Scale
- How do I Exit the Viewer and Get Back to the Home Page?
What is the TCEQ USGS Topographic Map Viewer?
This Viewer has been designed to provide interactive online access to the U.S. Geological Survey (USGS) 7.5-Minute Topographic Maps for the State of Texas. Several tools have been provided enabling you to zoom, pan, query, print, and obtain geographic coordinates. This help page provides a brief explanation of these tools. Several reference layers such as counties and roads have been provided to guide you to your area of interest. As you zoom in closer, more layers will appear. Once you have zoomed in past the scale of 1:75,000, the reference layers will disappear and the 7.5-Minute USGS Topograghic Maps will be visible along with the 7.5-minute and Digital Orthophoto Quarter Quad (DOQQ) indexes.
How do I Find the Name of a Particular Map Feature?
To find the name and other information associated with a particular map feature, you must first select the circular "radio button" next the layer for which you are interested. Once the layer is active, select the Identify Tool, then click the on the map feature. The name and other associated information will appear in a table at the bottom of the viewer.
What Do "Visible" and "Active" Mean?
In the map layers list there are "check boxes" and rounded "radio buttons" next to the name of each map layer. The checks in the boxes of the "Visible" column indicate which map layers are currently visible in the map frame. To turn a map layer off, simply uncheck its box and hit the Refresh button.
Obtaining a Latitude and Longitude
At any scale, you can obtain the latitude and longitude in both decimal degrees and degree-minutes-seconds by selecting on the XY button and then clicking anywhere on the map. A separate window will display the coordinates (unfortunately in Netscape, this window will open to the full extent of the page). Once you have recorded the latitude and longitude, close the page.
Note: Although the USGS Topo maps are referenced to the North American Datum of 1927 (NAD27), these coordinates are being converted to NAD83 on-the-fly.
Navigation Tools: Moving Around Within the Map
Zoom In Tool
This tool allows you to zoom in. Each single-click increases the map scale by 50%, centering the map display on the point clicked. To zoom to a selected area, hold the left mouse button down and draw a rectangle around the area you're interested in.
Zoom Out Tool
This tool allows you to zoom out. Each single-click decreases the map scale by 50%, centering the map display on the point clicked.
Zoom to Full Extent
This tool allows you to zoom to the full extent of the Texas.
Zoom to Active Layer
This tool allows you to zoom to the extent of the active layer.
Back to Last Extent
This tool allows you to zoom to the previous extent.
This tool allows you to measure distances on the map. After selecting the tool, click on the point from which you want to begin measuring (the starting point). Wait for a second until you see a red dot appear, then click on the next point. The length of this segment will appear in the boxes at the top of the screen. Extend the line by clicking on additional points. As you proceed, the length of the most recent segment will always appear in the second box named Segment. The total length of your line since the first point will appear in the first box named Total. If you want to erase and start over, just hit the Clear Selection button next to the printer button. Note: The units of measurement may be set by the Set Units tool.Set Units Tool
This tool allows you to set the display units. Display units affect both the Measure Tool and the Scale Bar. To set the units, select either meters, feet, miles, or kilometers from the drop-down list, then click the Set Units button.Clear Selection Tool
This tool allows you to clear any measuring lines currently on the map.
Selecting Features and Making Database Queries
This tool allows you to locate a map feature by entering a name ot other keyword into a text box. To do this, first make sure the appropriate layer is active, then click the Find button. A text box will appear at the bottom of the screen. Enter the word into the box, then click the Find String button or just hit the Enter key. Since a particular city or road may contain several polygons or lines, you may see several returns. Scroll to the bottom and click on "Zoom to these records" to zoom to the entire area represented by the records. Alternatively, you may click on indvidual Rec numbers to zoom to the different polygons or lines that make up that city or road. Click the clearhighlight_1.gif button to clear your selection.
Select by Rectangle Tool
IMPORTANT: This search tool is CASE SENSITIVE! If you are searching for a city, the first letter must be capitalized. It must also be spelled exactly as it appears in the associated database.
This tool allows you to select a feature or several features by drawing a box on the map. First make sure the approriate layer is active by selecting its rounded radio button. Next, click the Select By Rectangle tool in the toolbar. On the map, click-and-drag a box around the features you would like to select. At this point, the selected features will become highlighted and the database information for each of those features will appear at the bottom the screen. As with the Find tool, you may now zoom to these features by scrolling to the bottom and clicking on "Zoom to these records" or click the individual Rec number to zoom to a particular feature. Click the clearhighlight_1.gif button to clear your selection.
This tool allows you to print the current view. When you select the button, instructions for printing will appear at the bottom of the screen. You will be prompted for a title which will appear at the top of your map. As soon as you hit the Preview Map button, a new window will open displaying the map that will be printed. At this point, simply use the print button on your browser to send the map to the printer.
Zoom To Scale
Below the layer list is a drop-down menu allowing you to select a scale. Once you have centeredthe map over the area of interest, select the desired scale from the list and click on the Go! button. The map frame will immediately zoom to the selected scale. The USGS Topographic Quadrangle Maps have a source scale of 1:24,000. Therefore, if want to print out a map using the exact scale used on the paper 7.5-minute Topographic Map Sheets, you first zoom to 1:24,000.
To Exit the Viewer and Return to the Home Page.
When you are ready to leave the viewer, simply hit the Exit button in the lower left. A message will appear asking you to confirm your intent to exit the viewer. Click "Yes" to close the viewer. Once the viewer closes, a new window will appear taking you back to the TCEQ USGS Topographic Viewer Home Page. You may also click on the TCEQ logo which opens a separate window to the External TCEQ Home Page, but will not exit the viewer.
Not sure where to begin? Here are a few steps to get you started.
- The first thing you will want to do is zoom-in to an area of interest. To do this, select the Zoom-In Tool, then either single-click on a location or click-n-drag a box over the area in which you are interested. As you zoom in, you will notice that additional map layers such as roads, lakes, and rivers appear on the screen. These are reference layers to help guide you to the appropriate area.
- Next use the Identify Tool to get the name or other information associated with a particular map feature. For instance, you may want to identify name of a particular road. To do this, you must first select the rounded "radio button" next the roads map layer to make it Active (Note: You must be at the proper zoom level to see the roads). Next, click the Identify Tool from the toolbar menu on the left, then click on any road on the map to determine the name. The name and other relative information will appear in a table at the bottom of the viewer. The identify tool can be used on any map layer visible in the map frame, however, you must always first click the radio button of the layer and also verify that the identify tool is selected before clicking on a map feature.
- 3) Now zoom in closer. Once you have zoomed-in beyond the scale of 1:75,000, most of the reference map layers will vanish and the 7.5' USGS Topographic Quad Maps will appear. Two reference layers will remain visible on top of the Topo Maps: The 7.5-minute Quad Index and the Digital Orthophoto Quarter Quad Grid. Make the Quad Index Layer active by clicking on its radio button, click on the identify tool, and then click on any point on the map. You will see the name and USGS Quad number for that particular quad appear at the bottom on the screen. Now make the DOQQ Quad Index active. Again, use the identify tool to select a point on the map. This time the Quarter Quad name, EISYS number, and extended USGS number will appear. DOQQs, which are digital versions of aerial imagery, are often stored using the EISYS (Earth Information Systems) number.
- For the next step, locate any point on the map for which you
would like to acquire geographic coordinates. Click on the
XY Tool to the left of the map frame and then
click on your point of interest (Internet Explorer will give you
crosshairs, but Netscape will not). When you click on the map, a
separate window will appear giving you the latitude and longitude
of the point in both in Degrees-Minutes-Seconds and Decimal
Degrees. Click the X in the upper right-hand corner to dismiss the
Note: The original datum used for the 7.5" USGS Topo Maps is NAD27 (North American Datum of 1927). The XY Tool converts these coordinates to NAD83 on-the-fly. NAD83 is the datum which should be used for all data collected within the agency.
- Now let's say you want to measure the distance between two
sites. First zoom-in to the area of interest. Next, click on the
Tool. The "Set Units" page will appear at the bottom of
the screen. By default, the units are set to Miles. Click on the
drop-down list and select Meters, then click the Set
Units button in the center. Notice that the scale bar
units have now changed to meters. Now click on the Measure Tool, then click
on the first site you want to measure. Wait for a second to make
sure a red dot appears on the screen where you clicked. Place a
second point on the next site. The distance will appear in the
boxes at the top of the screen. Now place a third point somewhere.
Notice that the box named Total sums the entire distance
along you line from the first point. The second box, named
Segment, will show you only the length of the most recent
segment you added. Once you have recorded the distance, click on
the Clear Selection Tool to clear the
map of all line segments.
- Finally we are ready to print out our map. While still in your area of interest, click the drop-down list under Zoom To Scale and select 1:24,000. At this scale, the information on the topograghic maps be will more discernable. It will also match the scale of the paper 7.5-minute topographic maps. Hit the Go! button and the map frame will zoom to the selected scale. Now hit the Print Tool. Instructions for printing will appear at the bottom of the screen. With your mouse, swipe over the text that reads "Enter map title here" and type in a new title. Hit the Preview Map button. A new window will open displaying the map and its new title. From here, simply hit the browser's print button to send your map to the printer. Close the window to resume your session.
- To exit the viewer, just click on Exit at the bottom left part of the viewer. A box will pop up asking if you are sure you want to leave. Hit Yes to exit the viewer and return to the TCEQ USGS Topographic Viewer Home Page.